Catheter pump introducer systems and methods

ABSTRACT

A catheter system for a catheter pump is disclosed. The system can include an elongate catheter body having a distal portion including an expandable cannula having an inlet and an outlet. The expandable cannula can have a delivery profile and an operational profile larger than the delivery profile. An impeller assembly can include an impeller shaft and an impeller body. A sheath can have a cannula retention zone disposed over the expandable cannula and a separation zone. The cannula retention zone can have a first configuration adapted to retain the expandable cannula in the delivery profile. The system can be adapted to separate the separation zone into a first portion and a second portion disposed across a gap. The gap can enable the elongate catheter body to pass between the first and second portion so that the sheath can be removed from the elongate catheter body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/979,937, filed Apr. 15, 2014, the contents of which areincorporated by reference herein in their entirety and for all purposes.

BACKGROUND OF THE INVENTION

Field of the Invention

This application is directed to pumps for mechanical circulatory supportof a heart. In particular, this application is directed to devices usedto position such pumps in a patient using percutaneous or cathetertechniques.

Description of the Related Art

Heart disease is a major health problem that has high mortality rate.Physicians increasingly use mechanical circulatory support systems fortreating heart failure. The treatment of acute heart failure requires adevice that can provide support to the patient quickly. Physiciansdesire treatment options that can be deployed quickly andminimally-invasively.

Intra-aortic balloon pumps (IABP) are currently the most common type ofcirculatory support devices for treating acute heart failure. IABPs arecommonly used to treat heart failure, such as to stabilize a patientafter cardiogenic shock, during treatment of acute myocardial infarction(MI) or decompensated heart failure, or to support a patient during highrisk percutaneous coronary intervention (PCI). Circulatory supportsystems may be used alone or with pharmacological treatment.

In a conventional approach, an IABP is positioned in the aorta andactuated in a counterpulsation fashion to provide partial support to thecirculatory system. More recently minimally-invasive rotary blood pumphave been developed in an attempt to increase the level of potentialsupport (i.e. higher flow). A rotary blood pump is typically insertedinto the body and connected to the cardiovascular system, for example,to the left ventricle and the ascending aorta to assist the pumpingfunction of the heart. Other known applications pumping venous bloodfrom the right ventricle to the pulmonary artery for support of theright side of the heart. An aim of acute circulatory support devices isto reduce the load on the heart muscle for a period of time, tostabilize the patient prior to heart transplant or for continuingsupport.

There is a need for improved mechanical circulatory support devices fortreating acute heart failure. Fixed cross-section ventricular assistdevices designed to provide near full heart flow rate are either toolarge to be advanced percutaneously (e.g., through the femoral arterywithout a cutdown) or provide insufficient flow.

There is a need for a pump with improved performance and clinicaloutcomes. There is a need for a pump that can provide elevated flowrates with reduced risk of hemolysis and thrombosis. There is a need fora pump that can be inserted minimally-invasively and provide sufficientflow rates for various indications while reducing the risk of majoradverse events. In one aspect, there is a need for a heart pump that canbe placed minimally-invasively, for example, through a 15FR or 12FRincision. In one aspect, there is a need for a heart pump that can beplaced minimally-invasively and provide high flow rates but minimizeobstruction of the vasculature through which the pump is placed. In oneaspect, there is a need for a heart pump that can provide an averageflow rate of 4 Lpm or more during operation, for example, at 62 mmHg ofhead pressure. While the flow rate of a rotary pump can be increased byrotating the impeller faster, higher rotational speeds are known toincrease the risk of hemolysis, which can lead to adverse outcomes andin some cases death. Accordingly, in one aspect, there is a need for apump that can provide sufficient flow while minimizing the likelihood ofhemolysis at high rotational speeds. These and other problems areovercome by the inventions described herein.

Further, there is a need for providing an operative device of the pumpcapable of pumping blood at high flow rates while reducing the risk ofhemolysis at the operative device. For example, when an impellerassembly is provided at the operative device, the high rate of rotationof the impeller may cause hemolysis, as blood flows past the high-speedimpeller. Accordingly, there is a need for reducing the risk ofhemolysis at the operative device of the pump, particularly when movablecomponents are disposed at the operative device.

SUMMARY

There is an urgent need for a pumping device that can be insertedpercutaneously and also provide full cardiac rate flows of the left,right, or both the left and right sides of the heart when called for.

In one embodiment, a catheter system for a catheter pump is providedthat includes an elongate body an impeller assembly, and a sheath. Theelongated catheter body has a distal portion that includes an expandablecannula. The expandable cannula has an inlet and an outlet. Theexpandable cannula has a delivery profile and an operational profilelarger than the delivery profile. The impeller assembly includes animpeller shaft and an impeller body that includes one or more blades.The impeller blade(s) draw fluid blood into the cannula when rotated inthe fluid. The sheath has a cannula retention zone disposed over theexpandable cannula and a separation zone. The cannula retention zone hasa first configuration in which it is adapted to retain the expandablecannula in the delivery profile. The wherein the system is adapted toseparate the separation zone into a first portion and a second portiondisposed across a gap, the gap enabling the elongate catheter body topass between the first and second portion so that the sheath can beremoved from the elongate catheter body.

In another embodiment, a method is disclosed. The method can compriseadvancing into the vasculature a catheter assembly. The catheterassembly can include an expandable cannula having an expandable impellerdisposed therein and a sheath having a cannula retention portiondisposed over the expandable cannula and the expandable impeller. Thecannula retention portion can retain the expandable cannula and theexpandable impeller in a low profile configuration. The method canfurther include providing relative motion between the sheath and theexpandable cannula to expose the expandable cannula to permit theexpandable cannula to expand to a high profile configuration. The highprofile configuration can have a larger width than the low profileconfiguration. The first and second portions of the sheath can beseparated along a longitudinal portion thereof to create a gaptherealong. The method can include passing the elongate body through thegap to cause the sheath to be removed from the catheter assembly.

In yet another embodiment, a method is disclosed. The method cancomprise disposing an introducer sheath in the vasculature of a patient.The method can include introducing a catheter assembly into the proximalend of the introducer sheath and into the vasculature through theintroducer sheath. The catheter assembly can include an elongate bodyhaving an expandable cannula coupled with a distal end thereof. Thecatheter assembly can have an expandable impeller being journaled forrotation in the expandable cannula. The expandable impeller can beexpanded for operation in a source of blood. The elongate body can beretracted into the introducer sheath such that the expandable cannulaengages a distal end of the introducer sheath. Relative motion can beprovided between the introducer sheath and the expandable cannula tocompress the expandable cannula. The introducer sheath and the catheterassembly can be removed from the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of this applicationand the various advantages thereof can be realized by reference to thefollowing detailed description, in which reference is made to theaccompanying drawings in which:

FIG. 1 illustrates one embodiment of an extracorporeal portion of acatheter pump configured for percutaneous application and operation;

FIG. 2 is a plan view of one embodiment of a catheter assembly adaptedto be used with the catheter pump of FIG. 1, a distal portion of whichis inserted into the vasculature of a patient in use;

FIGS. 3A-3C illustrate the relative position of an impeller blade and aninner surface of an impeller housing or cannula in an undeflectedconfiguration;

FIG. 4 shows the catheter assembly similar to that of FIG. 2 in positionwithin the anatomy;

FIG. 5 shows an embodiment of a catheter assembly similar to that ofFIG. 2 with a sheath that can be removed from the vasculature of apatient while the working end of the pump is in operation;

FIG. 5A shows a graph of an axial force that may be required to beapplied to an outer sheath;

FIG. 6 shows a simplified embodiment of a catheter assembly with asheath that can be removed from the vasculature of a patient while theworking end of the pump is in operation;

FIGS. 7 & 7A illustrate more details of a removeable sheath and therelationship of the sheath to components that it houses duringintroduction; and

FIGS. 8-13 illustrate methods of using a catheter assembly including aremoveable sheath assembly as discussed herein.

More detailed descriptions of various embodiments of components forheart pumps useful to treat patients experiencing cardiac stress,including acute heart failure, are set forth below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This application is directed to apparatuses for inducing motion of afluid relative to the apparatus. In particular, the disclosedembodiments generally relate to various configurations of devices forpercutaneously delivering a distal portion of a catheter pump. Asdiscussed in greater detail below, such devices provide reduced orminimized blood flow obstruction in the vasculature in which thecatheter pump is disposed. For example, in the disclosed embodiments,one or more layers of a distal portion of the catheter assembly can beremoved to reduce the profile of the distal portion during operation ofthe pump. In some embodiments a temporary protector is provided forexpandable and/or delicate structures of a catheter pump assembly. Insome of the disclosed embodiments, the function of collapsing anexpandable portion of the catheter pump and of providing initial accessto the vasculature is performed by the same structure.

I. Catheter Pump System and Method

FIGS. 1-4 show aspects of one embodiment of a catheter pump 10 that canprovide high performance flow rates. Various additional aspects of thepump and associated components are similar to those disclosed in U.S.Pat. Nos. 7,393,181, 8,376,707, 7,841,976, 8,535,211, 8,597,170,8,485,961, 8,591,393, 7,022,100, and 7,998,054 and U.S. Pub. Nos.2012/0178986, 2013/0303970, 2013/0303969, 2013/0303830, 2014/0012065,and 2014/0010686 the entire contents of which are incorporated hereinfor all purposes by reference. In addition, this applicationincorporates by reference in its entirety and for all purposes thesubject matter disclosed in each of the following concurrently filedapplications: U.S. patent application Ser. Nos. 14/203,978, whichcorresponds to attorney docket no. THOR.084A, entitled “FLUID HANDLINGSYSTEM,” and 14/209,889, which corresponds to attorney docket no.THOR.097A, entitled “CATHETER PUMP ASSEMBLY INCLUDING A STATOR,” filedon Mar. 13, 2014 and PCT Patent Application Nos. PCT/US2014/020790 whichcorresponds to attorney docket no. THOR.084WO, entitled “FLUID HANDLINGSYSTEM,” and PCT/US2014/020878 which corresponds to attorney docket no.THOR.097WO, entitled “CATHETER PUMP ASSEMBLY INCLUDING A STATOR,” filedon Mar. 5, 2014.

A. Catheter Pump System

The pump 10 includes a motor driven by a controller 22. The controller22 directs the operation of the motor 14 and an infusion system 26 thatsupplies a flow of infusate in the pump 10. A catheter system 80 thatcan be coupled with the motor 14 houses an impeller within a distalportion thereof. The catheter system 80 has a coupling 90 that can beengaged with the motor 14 in certain embodiments. In variousembodiments, the impeller is rotated by the motor 14 when the pump 10 isoperating. For example, the motor 14 can be disposed outside thepatient. In some embodiments, the motor 14 is separate from thecontroller 22, e.g., to be placed closer to the patient. In otherembodiments, the motor 14 is part of the controller 22. In still otherembodiments, the motor is miniaturized to be insertable into thepatient. Such embodiments allow the drive shaft to be much shorter,e.g., shorter than the distance from the aortic valve to the aortic arch(about 5 cm or less). Some examples of miniaturized motors catheterpumps and related components and methods are discussed in U.S. Pat. Nos.5,964,694; 6,007,478; 6,178,922; and 6,176,848, all of which are herebyincorporated by reference herein in their entirety for all purposes.

FIG. 2 shows features that facilitate small blood vessel percutaneousdelivery of a high performance pump head, including a pump head capableof producing up to and in some cases exceeding normal cardiac output inall phases of the cardiac cycle. In particular, the catheter system 80includes a catheter body 84 and a sheath assembly 88. In one embodimenta blood flow assembly 92 (sometimes referred to herein as an impellerassembly) is coupled with the distal end of the catheter body 84. Atleast a portion of the blood flow assembly 92 is expandable andcollapsible. For example, the blood flow assembly 92 can include anexpandable and collapsible cannula 202. The cannula 202 can be formed ofa superelastic material, and in some embodiments, may have various shapememory material properties. The blood flow assembly 92 also can includean expandable and collapsible impeller 300 (see FIGS. 3B-3C). Thecannula 202 and impeller 300 are discussed more below. In the collapsedstate, the distal end of the catheter system 80 can be advanced to theheart, for example, through an artery. In the expanded state the bloodflow assembly 92 is able to pump or output blood at high flow rates.FIGS. 2-4 illustrate the expanded state of one embodiment. The collapsedstate can be provided by advancing a distal end 94 of an elongate body96 of the sheath assembly 88 distally over the cannula of the blood flowassembly 92 to cause the blood flow assembly 92 to collapse. Inembodiments below, variations of the sheath assembly 88 can be removedat least in part. In one variation discussed further below, a separationdevice 500 is provided on the catheter system 80 to induce or easesegmentation of the sheath assembly 88 or portions thereof into separateparts. The separation device 500 can include one or more fins that aredisposed on the proximal portion of the elongate body 84 of the cathetersystem 80. The fins can be rigid protrusions of disposed on at leastpartially on the body 84 or disposed on a portion of the coupling 90.The separation device 500 can be disposed at least in part on a strainrelief portion disposed between the coupling 90 and the elongate body84. As discussed further below, in such embodiments other structures areused to collapse the cannula 202 and the impeller 300 after thesecomponents are expanded inside the patient. This provides an outerprofile throughout the catheter assembly 80 that is of small diameter,for example a catheter size of about 12.5 Fr. This also provides thatthe operational profile of the catheter assembly can be reduced orminimized as discussed further below.

B. Impeller and Cannula Features, Deployment, and Operation

With reference to FIGS. 3A-3C, the operative device of the pump caninclude the impeller 300, which has one or more blades 303. The one ormore blades 303 can extend from an impeller hub 301. It can be desirableto increase the flow rate of the heart pump while ensuring that theimpeller 300 can be effectively deployed within a subject. For example,an impeller can include one or more blades 303 that are configured to beinserted into a subject in a stored, or compressed, configuration. Whenthe impeller 300 is positioned in the desired location, e.g., a chamberof a subject's heart as shown in FIG. 4, the blade(s) 303 of theimpeller 300 can self-expand into a deployed or expanded configuration,in which the blade(s) 303 extends radially from a hub 301.

As shown in FIGS. 3A-3B, the impeller 300 can be positioned within thecannula or housing 202. A free end of the blades 303 can be separatedfrom the wall W of the housing 202 by a tip gap G. The housing 202 canalso have a stored, or compressed configuration, and a deployed orexpanded configuration. The housing 202 and impeller 300 may deploy fromthe stored configurations from within the sheath assembly 88 into theexpanded configuration. In such implementations, the sheath assembly 88can keep the blade(s) 303 and the housing 202 compressed until theblade(s) 303 and housing 202 are urged from within a lumen of the sheathassembly 88. Once the blade(s) 303 are released from the sheathassembly, the blade(s) 303 can self-expand to a deployed configurationusing strain energy stored in the blades 303 due to deformation of theblade(s) 303 within the sheath assembly 88. The expandable housing 202may also self-deploy using stored strain energy after being urged fromthe sheath. The combined energy stored in the expandable housing 202 andblades 303 generates a force that preferably is opposed by the distalportion of the elongate body 96 of the sheath assembly 88. Thus, thisportion should be of robust design to avoid premature deployment of thehousing 202 and blades 303, e.g., prior to positioning in the heart orother source of blood.

Variations of the sheath assembly 88 are configured to be removed (e.g.,by one or more seams) from the patient's body and in some cases entirelyfrom the catheter body 84 to lower the profile of the portion of thecatheter system 80 in the body. Removing the sheath assembly 88 has anumber of benefits discussed further below including opening up space inthe vasculature for blood flow around the remainder of the cathetersystem 80 that remains in the vasculature after the sheath assembly isremoved. By providing such additional flow, the ability of the patientto tolerate the presence of the implanted portions of the pump 10 isenhanced. Catheter pumps typically have a large diameter relative to theaccess vessels and thus pose a meaningful risk of limb ischemia andother complications. Accordingly, even small reductions in diameter andincreased blood flow around the device can be advantageous. Also, byenabling a portion of the catheter pump that is initially placed in theaccess vessel to be removed, a less invasive access technique can beprovided. For example, the skin and blood vessel puncture can be smallerin size be removing one or more layers during or shortly after placementof the pump. For example, the presence of the body of the sheathcontributes to the overall profile of the assembly passing through theskin and into the blood vessel. The skin and blood vessel can stretchfor a short time which can enable the puncture to be the same size oreven a bit smaller than the initial profile of the catheter assembly. Byremoving the sheath 88, the degree of stretch, the time during which thepunctured tissues are stretched or both the degree and time are reducedwhich enables the punctures to be smaller and/or to avoid surgicalcut-down while maintaining the size of the internal components (e.g.,cannula, impeller, and drive shaft). These and other benefits andstructures are discussed further below.

In the stored configuration, the impeller 300 and housing 202 have adiameter that is preferably small enough to be inserted percutaneouslyinto a patient's vascular system. Thus, it can be advantageous to foldthe impeller 300 and housing 202 into a small enough storedconfiguration such that the housing 202 and impeller 300 can fit withinthe patient's veins or arteries, particularly small veins or arteriesthat are peripheral and superficial, e.g., femoral veins or arteries,jugular and subclavian veins, radial and subclavian arteries. In someembodiments, therefore, the impeller 300 can have a diameter in thestored configuration corresponding to a catheter size between about 8 Frand about 21 Fr. In one implementation, the impeller 300 can have adiameter in the stored state corresponding to a catheter size of about 7Fr. In one implementation, the impeller 300 can have a diameter in thestored state corresponding to a catheter size of about 9 Fr. In oneimplementation, the impeller 300 can have a diameter in the stored statecorresponding to a catheter size of about 10 Fr. In other embodiments,the impeller 300 can have a diameter in the stored configuration betweenabout 12 Fr and about 21 Fr. For example, in one embodiment, theimpeller 300 can have a diameter in the stored configurationcorresponding to a catheter size of about 12-12.5 Fr.

When the impeller 300 is positioned within a chamber of the heart,however, it can be advantageous to expand the impeller 300 to have adiameter as large as possible in the expanded or deployed configuration.In general, increased diameter of the impeller 300 advantageouslyincreases flow rate through the pump at a given rotational speed. Alarger diameter impeller can also lead to an improved ratio of flow rateto hemolysis rate. In some implementations, the impeller 300 can have adiameter corresponding to a catheter size greater than about 12 Fr inthe deployed configuration. In other embodiments, the impeller 300 canhave a diameter corresponding to a catheter size greater than about 21Fr in the deployed or expanded configuration.

In various embodiments, it can be important to increase the flow rate ofthe heart pump while ensuring that the operation of the pump does notharm the subject. For example, increased flow rate of the heart pump canadvantageously yield better outcomes for a patient by improving thecirculation of blood within the patient. Furthermore, the pump shouldavoid damaging the subject. For example, if the pump induces excessiveshear stresses on the blood and fluid flowing through the pump (e.g.,flowing through the cannula), then the impeller can cause damage toblood cells, e.g., hemolysis. A high hemolysis rate over an extendedperiod can lead to negative outcomes and complications for the subjectlike stroke, excessive bleeding, anemia, and hypertension. Also, thepresence of the distal portion of the catheter system 80 within the bodyis at least partially obstructive. That is, the catheter body 84 blocksflow to an extent, e.g., to peripheral regions of the body and smallerbranch arteries when applied in the arterial vasculature. The distal end94 of the sheath assembly 88 also presents a blocking surface to bloodfollowing the outer surface of the body 84. As will be explained below,various cannula, system, and/or impeller parameters can affect thepump's flow rate as well as conditions within the subject's body.

When activated, the pump 10 can effectively increase the flow of bloodout of the heart and through the patient's vascular system. In variousembodiments disclosed herein, the pump 10 can be configured to produce amaximum flow rate (e.g. low mm Hg) of greater than 4 Lpm, greater than4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, greater than 6 Lpm,greater than 6.5 Lpm, greater than 7 Lpm, greater than 7.5 Lpm, greaterthan 8 Lpm, greater than 9 Lpm, or greater than 10 Lpm. In variousembodiments, the pump can be configured to produce an average flow rateof greater than 2 Lpm, greater than 2.5 Lpm, greater than 3 Lpm, greaterthan 3.5 Lpm, greater than 4 Lpm, greater than 4.25 Lpm, greater than4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, or greater than 6Lpm.

C. Exemplary Left Ventricle Support Application

FIG. 4 illustrates one use of the catheter pump 10. A distal portion ofthe pump 10, which can include an impeller assembly 92, is placed in theleft ventricle (LV) of the heart to pump blood from the LV into theaorta. The pump 10 can be used in this way to treat patients with a widerange of conditions, including cardiogenic shock, myocardial infarction,and other cardiac conditions, and also to support a patient during aprocedure such as percutaneous coronary intervention. One convenientmanner of placement of the distal portion of the pump 10 in the heart isby percutaneous access and delivery using the Seldinger technique orother methods familiar to cardiologists. These approaches enable thepump 10 to be used in emergency medicine, a catheter lab and in othernon-surgical settings. Inventive variations of these methods arediscussed in connection with FIGS. 13-18 below. Modifications can alsoenable the pump 10 to support the right side of the heart. Examplemodifications that could be used for right side support includeproviding delivery features and/or shaping a distal portion that is tobe placed through at least one heart valve from the venous side, such asis discussed in U.S. Patent and Patent Publication Nos. 6,544,216; U.S.Pat No. 7,070,555; and US 2012-0203056A1, all of which are herebyincorporated by reference herein in their entirety for all purposes.

II. Reducing the Catheter Assembly Profile in Operation

As noted above, one aspect of biocompatibility of the pump 10 is thedegree to which it obstructs blood flow in the patient. That is, thecatheter assembly 80 takes up some of the cross-sectional area of theblood vessels in which it is disposed. If the space occupied by one ormore layers can be reduced or eliminated in one or more phases ofoperation of the pump 10 the flow of blood through the vasculature inwhich the pump is disposed and to branch vessels will be improved.Furthermore, while the sheath assembly 88 is very useful in maintainingthe impeller assembly 92 in a low profile configuration for delivery, itis unnecessary during the actual operation of the pump 10. Because thedistal end 94 of the sheath assembly 88 has some thickness it willnecessarily create blockage and a disturbance in the flow of blood alongthe catheter body 84. That is blood may be flow in an organized manneralong the body 84 just upstream of the distal end 94 but will bedisrupted at the distal face of the distal end 94.

A. Removable Retainer For Impeller Assembly

FIG. 5 shows a catheter assembly 400 similar to the catheter assembly 80except that the catheter assembly 400 is made lower profile byconfiguring at least one layer to be removed before or during operationof the pump. The assembly 400 includes a sheath assembly 404 that can bedisposed over the catheter body 84. The sheath assembly 404 includes adistal end 408, a proximal end 412, and an elongate body 416 thatextends between the distal and proximal ends 408, 412. The elongate body416 has at least one lumen disposed therein. A lumen in the elongatebody 416 can house the elongate body 84 of the catheter assembly 400.The elongate body 84 can be disposed in the lumen of the elongate body416 permitting relative movement of the elongate bodies 84, 416 asdiscussed below. In one embodiment, a lumen is provided in the elongatebody 416 for sensing pressure at the distal end 408. In one embodiment,a pressure sensing lumen is contiguous with the lumen within which theelongate body 84 is disposed. In one embodiment, a pressure sensinglumen is separate from the lumen within which the elongate body 84 isdisposed.

At least a portion of the sheath assembly 404 is configured to separatefrom the elongate body 84 in a controlled manner at a selected time.This enables the catheter assembly 400 to be delivered as discussedbelow and then to permit the sheath assembly 404 to be removed from thebody. In one embodiment, a separation zone 420 is provided along theelongate body 416 to enable the elongate body 416 to be opened such thatthe elongate body 84 can pass through the separation zone 420. In oneembodiment, the separation zone 420 enables the elongate body 416 to beseparated into a plurality of pieces or segments. In one embodiment, theseparation zone 420 comprises a linear seam disposed along the elongatebody 416. The separation zone 420 comprises two seams in one embodiment,one of the seams disposed along a first later side of the elongate body416 and another of the seams disposed along a second later side of theelongate body 416. Two of a plurality of seams can be disposed at 180degrees apart from each other on the elongate body 416. FIGS. 7 and 7Aillustrate opposed seams in more detail, as discussed further below. Inone embodiment the separation zone 420 extends from the distal end 408proximally toward, and in some cases entirely to, the proximal end 412.In another embodiment, the separation zone 420 extends from the proximalend 412 toward the distal end 404 of the elongate body 416.

The separation zone or zones 420 can have any suitable configurationthat facilities separating the elongate body 416 into a plurality ofpieces or that facilitates changing the configuration of the elongatebody 416 from a tubular body to one or more sheet-like body. Anadvantage of such separation is that the sheath assembly 404 can beremoved from the catheter assembly 400 without removing the motorcoupling 90 from the proximal end of the system 400 and without greatlylengthening the elongate body 84.

In another embodiment, the separation zone 420 extends along theelongate body 416 and has a distal end that is proximal of the distalend 404. By spacing the distal end of the separation zone 420 from thedistal end 408 of the elongate body 416 the outward load or shear orseparation force that can be borne by the elongate body 416 can begreater adjacent to the distal end thereof. In one embodiment, theelongate body 416 can be configured such that a first outward force, orshear or separation force can be borne in a region adjacent to theproximal end 412 and a second outward force, shear, or separation forcegreater than the first outward force, shear, or separation force can beborne by the elongate body 416 adjacent to the distal end 408.

Different outward, shear, or separation force capability can be providedin any suitable manner. For example, the separation zone 420 can have afirst seam in a proximal portion of the elongate body 416 and a secondseam in a distal portion of the elongate body 416. The first and secondseams can be disposed along a continuous line or plane, e.g., along anaxis parallel to the longitudinal axis of the elongate body 416. Thefirst seam can have a first plurality of bridges separated by space andthe second seams can have a second plurality of bridges separated byspace, the dimension of the bridges along the longitudinal axis beinggreater in the second seam than in the first seam. The first seam canhave a first plurality of bridges spanning between and coupling expansesof the elongate body 416 on opposite sides of the separation zone, thebridges being separated by space. The second seams can have a secondplurality of such bridges separated by space. The dimension of thebridges along the longitudinal axis of the separation zone 420 can begreater in the second seam than in the first seam. In anotherembodiment, the radial thickness (e.g., wall thickness or dimensiontransverse to the longitudinal axis) is greater in the second seam thanin the first seam.

In one embodiment, a first lateral separation zone is provided along afirst lateral side of the elongate body 416 and a second lateralseparation zone is provided along a second lateral side of the elongatebody 416. The first and second lateral sides can oppose each other,e.g., by being about 180 degrees apart. This is illustrated inconnection with the embodiment of FIGS. 7 and 7A. The first and secondlateral separation zones can each have a composite seam. The compositeseam can include a first portion adjacent the proximal end and a secondportion adjacent to the distal end. The second portion can have a higherresistance to separation along the second portion than is provided inthe first portion. By providing higher resistance to separation towardthe distal end of the sheath assembly 404, e.g., with a composite seam,the sheath assembly can be configured to bear the outwardly directedload from the impeller assembly 92 without inadvertently or prematurelytearing or separating. In some embodiments, the sheath assembly can beconfigured such that a tear away or separation force is small enough tofacilitate separation or tearing by a user, while remaining high enoughsuch that the cannula expansion force does not prematurely inducetearing or separation. For example, the assembly can be configured suchthat the tearing or separation force can be greater than the forcesillustrated in FIG. 5A. FIG. 5A shows a graph of an axial force that maybe required to be applied to an outer sheath, such as by the sheathassembly 88, disposed about the catheter body as the sheath assembly 88is advanced distally along the cannula. Additional details associatedwith FIG. 5A may be found in FIG. 17 and described in the associateddisclosure of U.S. Patent Publication No. US 2014/0012065, which isincorporated by reference herein in its entirety and for all purposes.

FIG. 5 shows that the sheath assembly 404 can include a side branch 432extending from a hub 436. The side branch 432 can serve one or more ofseveral purposes. For example, the side branch 432 can have a lumen influid communication with a lumen disposed within the elongate body 416.A fluid connector can be disposed at the proximal end of the side branch432 to couple the side branch with another device, such as a source offluid. The fluid from the source of fluid can be directed into the sidebranch 432 and thereafter into a lumen in the elongate body 416. Suchfluid can be used to reduce the force needed to provide relative motionbetween the elongate body 84 and the elongate body 416. The lumen withinthe side branch 432 can have a pressure sensing function. For example,the side branch 432 can be in fluid communication with a pressuresensing device or lumen disposed in the elongate body 416. Such asensing lumen can be used to track the position of the distal end of thecatheter assembly 400.

FIG. 6 shows a simplified embodiment of a catheter assembly 450 with asheath assembly 454 that can be removed from a patient while the workingend of the pump 10 including the catheter assembly 450 is in operation.The sheath assembly 454 is similar to the sheath assembly 404 exceptthat it includes a low profile hub 456 without a side branch. The hub456 is disposed at a proximal end 462 opposite a distal end 458. The hub456 includes two lateral handles 464A, 464B that can be grasped by theclinician to provide relative movement of a body 466 of the sheatheassembly 454 over the elongate body 84. The lateral handles 464A, 464Bcan also be used to cause the hub 456 to separate into two pieces asdiscussed further below in connection with Figures and 7A. A separationzone in the hub 456 (e.g., a seam) is disposed immediately proximal ofand/or overlaps with a separation zone 470 (e.g., a seam) in the body466 of the sheath assembly 454. The separation zone 470 can be disposedat one or a plurality of locations about the body 466 and can becomposite in nature as discussed above.

FIGS. 7 and 7A convey further details of the sheath assembly 454. FIG. 7shows two configurations the sheath assembly 454. A first configurationis provided for delivering the catheter assembly 450 into the patient.That is, the body 466 and the hub 456 are intact. A circular inner andouter periphery can provided, at least in the elongate body 466 of thesheath assembly 454. The first configuration is shown by solid lines inthe hub 456 and a proximal portion of the body 466. A secondconfiguration is provided, as illustrated by the dashed lines in the hub456 and the proximal portion of the body 466 in which the handles 464A,464B are separated from each other. In the second configuration theproximal portion of the elongate body 466 is separated into at least twoportions or segments, i.e., a first segment 472A and a second segment472B. In some methods discuss below the separation shown in FIG. 7continues to the distal end of the separation zone 470.

FIGS. 7 and 7A illustrate further features. For example, the separationzone 470 can include a first portion 476 and a second portion 480. Thefirst portion 476 is disposed in a proximal portion of the elongate body466 and the second portion 480 is disposed in a distal portion of theelongate body 466. The proximal portion 476 has a lower resistance totearing. Accordingly, the proximal portion 476 is configured to resistrelatively low radially outward forces or pressures. Such configurationis suitable because the lower portion is not required to retain anycompressed structures. As a result, a relatively low force applied tothe handles 464A, 464B or to the proximal ends of the segments 472A,472B causes the handles and/or segments to separate to the second(dashed outer profile) configuration. The distal portion 480 has ahigher resistance to tearing. This is advantageous in that the distalportion 480 overlies the expandable cannula 202 and the expandableimpeller 300. The impeller and cannula store strain energy whencompressed and are continually pressing outwardly on the sheathassemblies 404, 454. Accordingly, by elevating the tear resistance inthe distal portion 480, the sheath assembly 454 will not inadvertentlyor prematurely be force open by the stored strain energy of the cannula202 and the impeller 300. FIG. 7A shows the packing of these componentswithin the distal portion 480. The impeller 300 is shown schematicallysomewhat enlarged in the impeller shape but when compressed would behighly deformed and compacted to be disposed within a projection of thebody 84 (shown in dashed lines) and also would be disposed within thecompressed cannula 202, which would also be compressed to be disposedwithin the body 84. Because these structures are generally compressed tobe contained within a volume having a radius of about one-half or lessthan the un-compressed radius, high outward forces are applied by thesecompressed structures on the distal portion of the body of the sheathassembles 404, 454.

FIGS. 7 and 7A show that the separation of the segments 472A, 472B canbe facilitated by one or more separation zones, e.g., one or moreunitary and/or composite seams. As used in this context a unitaryseparation zone or same is one that has a uniform resistance to tearingalong the length of the separation zone or seam. The separation zones470A, 470B can be opposed, e.g., on opposite sides of the sheath body466. The separation zones 470A, 470B can have a composite structure withmore resistance to tearing in the distal portion 480 than in theproximal portion 476.

B. Methods of Deployment of Catheter Pump with Removable Outer Sheaths

FIGS. 8-13 illustrate methods of applying catheter systems discussedherein. These images are schematic in order to simplify the illustrationbut would generally include the components discussed above andillustrated in the figures.

FIG. 8 shows a simplified diagram of the vasculature that is traversedin one technique for applying the catheter assembly 450. The catheterassembly 450 is shown in place in one operational configuration. Thecatheter body 84 which houses a drive cable to cause the impeller 300 torotate within the cannula 202 is disposed through an introducer sheathI. Between the catheter body 84 and the introducer sheath I is a sheathassembly, for example the sheath assembly 454. The sheath assembly 454is moveable over the elongate body 84 between a distal position in whichthe distal end of the body 466 is disposed over the cannula 202 and aproximal position which of the elongate body 466 of the sheath assembly454 is disposed proximal of the cannula 202. FIG. 8 shows the sheathassembly 454 in the proximal position. A separation zone 470A extendsalong a length of the body 466 of the sheath assembly 454. In someembodiments the separation zone 470A extends from the proximal end tothe distal end of the sheath assembly 454.

FIGS. 9-12 illustrates steps that enable the catheter assembly 450 to bepositioned as shown in FIG. 8. FIG. 9 shows that a guidewire G is placedthrough a small incision or a needle or other small cannula (not shown)into a peripheral vessel. The guidewire G is advanced from theperipheral access site toward the heart. The peripheral access site isgenerally the femoral artery, though other vessels could be used asdiscussed above. For example, on the venous side, the femoral vein orthe internal jugular vein could be accessed for supporting the rightside of the heart. FIG. 10 shows that the guidewire G provides an accesstool for inserting an introducer sheath I that provides a window intothe vasculature large enough to deliver the catheter assembly 450 (orvariants including the other catheter assemblies described herein). FIG.10 is exaggerated to show that the introducer sheath I can providesignificant obstruction of the blood vessel in which access is providedand also downstream of such vessels and locations.

FIG. 11 shows the introduction of the catheter assembly 450 into thevasculature through the introducer I. The catheter assembly 450generally extends proximally and distally of the illustration asindicated by the break lines. In the distal direction, the catheterassembly 450 is advanced up the descending aorta to ultimately bepositioned in the heart, as in FIGS. 4 and 8. An intermediate portion ofthe catheter assembly 450 including an intermediate portion of thesheath assembly 454 extends through the abdominal aorta (as shown) andinto the thoracic aorta (not shown). In these positions the body 466 ofthe sheath assembly 454 also provides some obstruction to blood flow inthe vasculature.

The impeller 300 and the cannula 202 are deployed by providing relativemotion between these components and a distal end of the body 466 of thesheath assembly 454. Once the distal end of the body of the sheathassembly 454 is disposed proximally of the proximal end of the cannula202 the cannula and the impeller 300 will have been permitted to expand.As this point, the sheath assembly 454 provides no role in the operationof the pump 10 and can be removed.

Removal of the sheath assembly 454 can be as illustrated and describedin connection with FIGS. 7 and 7A. For example, the handles 464A, 464Bwhich are disposed outside the body of the sheath assembly 454 can bepulled apart which commences the separation of the segments of thesheath assembly 454. Pulling the handles 464A, 464B apart can beaccomplished by applying a force transverse to the longitudinal axis ofthe body 466. In certain embodiments one or more fins 500 (see FIG. 2)can be provided to aid in separating the handles 464A, 464B and/or topropagate a gap in the separation zone or zones 470A, 470B. The fins 500can be used in a system where one or both of a proximal hub or elongatebody of a sheath are not pre-formed with a seam or other structure toreduce the tear force of the sheath. Thus, a catheter system can beconfigured to segment a sheath assembly even if the sheath assembly isnot specifically adapted to tear along a pre-formed zone. FIGS. 5 and 6show embodiments of the sheath assembly positioned 90 degrees from theposition in which the fins 500 would engage the separation zone orzones. In other words, a 90 degree relative rotation of the sheathassembly 90 relative to the elongate body 84 would align the fins 500with the separation zones 470, 470A, 470B. The fins 500 would play arole in initially separating the handles 464A, 464B by pulling theproximal face of the handles 464A, 464B into contact with the fins 500until the handles 464A, 464B separate from each other. The fins wouldthen further slide in the separation zone form a gap therein. The body84 of the catheter assembly 450 can be held in position while thehandles 464A, 464B are withdrawn and pulled laterally to furtherseparate the body 466 of the sheath assembly 454.

FIG. 12 shows a proximal portion of the body 84 of the catheter assembly450 extending out of the proximal end of the introducer I and distalportion of the body 84 exposed in the abdominal aorta distal of thedistal end of the introducer I. This configuration eliminates thethickness of the body 466 of the sheath assembly 454 between the distalend of the introducer I and the distal end of the position of the body466 as illustrated in FIG. 8. Eliminating this layer increases the spaceavailable for blood flow by at least about 5% and in some cases betweenabout 5% and about 15%. In other embodiments, eliminating the body 466increases the space available for flow by at least about 15% and in somecases between about 15% and about 20%. Eliminating the body 466decreases the degree of stretch of the tissues at the puncture site toreduce the likelihood of tearing and/or to eliminate the need forsurgical cutdown at the skin or blood vessel access site. In addition,the distal face of the sheath assembly 454 can generate flowdisturbances, can be an origin for thrombosis formation and can belodged on plaque when advanced or, if not operated properly, interferewith the aortic valve leaflets when advanced to collapse the cannula 202and impeller 300. Thus, eliminating the sheath assembly 454 after thecannula 202 is expanded and during operation of the impeller 300 canimprove the overall performance of the pump 10.

FIG. 13 illustrates a technique for collapsing the cannula 202 andimpeller 300 to remove them from the patient. In particular, after thepump 10 is halted and no longer operating to pump blood, the impeller300 is stationary in the cannula 202. The body 84 of the catheterassembly 450 can be retracted from outside the patient That is a pullingforce is applied to the proximal end of the body 84 to provide movementof the body 84 relative to the introducer I such that a distal portionof the body 84 is pulled across the aortic valve and out of the heart.The cannula 202 and impeller 300 are flexible and compressible and thusare atraumatic to the valve leaflets. Further retraction of the body 84pulls the distal end of the body 84 and cannula 202 with impeller 300disposed therein along the ascending aorta, over the aortic arch anddown the descending aorta. Further retraction of the body 84 pulls theproximal end of the cannula 202 into adjacency with the distal end ofthe introducer I as illustrated in FIG. 13. The introducer I isconfigured with sufficient stiffness at the distal end thereof tocompress the cannula. Although the introducer I has a bore large thanthe sheath body 466 so does not require as much compression to initiallyreceive the cannula 202 and impeller 300. In some embodiments, thedistal end of introducer I can be shaped to enhance the collapse of thecannula 202. For example, the distal end of the introducer I cancomprise shapes and arrangements similar to those illustrated in FIGS.17A-17D and the associated disclosure of US Patent Publication No. US2012/0178986, which is incorporated by reference herein in its entiretyand for all purposes.

In one variation, the impeller 300 is configured to be retracted into acollapsed position prior to the collapsing of the cannula 202. A driveshaft that is coupled with the impeller 300 can be provided with amechanism to shift the position of the impeller from a deployed position(as in FIG. 13) to a stored position within an interior space of thebody 84 or of a structure coupled with the body 84. Such structures arediscussed in more detail in U.S. Pat. No. 7,841,976 and in U.S. PatentPublication 2012/0178986 (also included as an Appendix), both of whichare incorporated by reference for further discussion of these featuresand in their entirety. By shifting the impeller 300 into this storedposition the stiffness of the distal portion of the catheter assembly450 can be greatly reduced. Reduced stiffness of the distal portion ofthe catheter assembly 450 makes the distal portion of the catheterassembly easier to extract from the patient in a biocompatible manner.

Once the distal portion of the catheter assembly 450 is disposed in theintroducer I the introducer I and the distal portion of the catheterassembly 450 can be removed sequentially or together.

Although the inventions herein have been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent inventions. It is therefore to be understood that numerousmodifications can be made to the illustrative embodiments and that otherarrangements can be devised without departing from the spirit and scopeof the present inventions as defined by the appended claims. Thus, it isintended that the present application cover the modifications andvariations of these embodiments and their equivalents.

1. A catheter system for a catheter pump, comprising: an elongatecatheter body having a distal portion including an expandable cannulahaving an inlet and an outlet, the expandable cannula having a deliveryprofile and an operational profile larger than the delivery profile; animpeller assembly including an impeller shaft and an impeller bodyincluding one or more blades, the impeller blade(s) drawing fluid intothe cannula when rotated in the fluid; a sheath having a cannularetention zone disposed over the expandable cannula and a separationzone, the cannula retention zone having a first configuration adapted toretain the expandable cannula in the delivery profile; wherein thesystem is adapted to separate the separation zone into a first portionand a second portion disposed across a gap, the gap enabling theelongate catheter body to pass between the first and second portion sothat the sheath can be removed from the elongate catheter body.
 2. Thecatheter system of claim 1, wherein the cannula retention zone comprisesa first resistance to tearing, the sheath having an elongate zoneproximal of the cannula retention zone having a second resistance totearing, the second resistance to tearing being lower than the firstresistance to tearing.
 3. The catheter system of claim 1, wherein theseparation zone includes a composite seam.
 4. The catheter system ofclaim 3, wherein the composite seam includes a first perforated segmentdisposed in the cannula retention zone and a second perforated segmentdisposed proximally of the cannula retention zone, the first perforatedsegment including perforations with less density than in the secondperforated segment.
 5. The catheter system of claim 1, wherein theseparation zone includes a first portion and a second portion opposed tothe first portion such that the sheath can be separated into twosegments.
 6. The catheter system of claim 5 wherein the first and secondportions are disposed on opposite sides of the body of the sheath. 7.The catheter system of claim 1,, further comprising handles disposed onthe proximal end of the sheath, the handles having a first configurationfor providing relative motion between the sheath and the elongate bodyand a second configuration for changing the configuration of the sheathfrom a tubular configuration to a sheet-like configuration.
 8. Thecatheter system of claim 1, wherein a separation device is disposed onthe catheter system proximal of the sheath at least when the cannularetention zone of the sheath is disposed over the expandable cannula. 9.The catheter system of claim 1, wherein the separation device comprisesat least one fin disposed on the elongate catheter body.
 10. Thecatheter system of claim 1, wherein the sheath includes a side branchhaving a lumen.
 11. The catheter system of claim 10, further comprisinga pressure sensing device adapted to detect pressure at the distal endof the sheath.
 12. The catheter system of claim 11, wherein the pressuresensing device is coupled with the proximal end of the side branch. 13.A method, comprising: advancing into the vasculature a catheter assemblyincluding an elongate body, an expandable cannula having an expandableimpeller disposed therein, and a sheath having a cannula retentionportion disposed over the expandable cannula and the expandableimpeller, the cannula retention portion retaining the expandable cannulaand the expandable impeller in a low profile configuration; providingrelative motion between the sheath and the expandable cannula to exposethe expandable cannula to permit the expandable cannula to expand to ahigh profile configuration, the high profile configuration having alarger width than the low profile configuration; separating first andsecond portions of the sheath along a longitudinal portion thereof tocreate a gap therealong; passing the elongate body through the gap tocause the sheath to be removed from the catheter assembly.
 14. Themethod of claim 13, further comprising separating first and secondportions of a handle assembly and pulling the first and second portionto extend a gap along the longitudinal direction of the sheath.
 15. Themethod of claim 13, further comprising pulling a separation zone intoengagement with a separation device disposed on a proximal portion of acatheter body of the catheter assembly, the catheter body being coupledwith the cannula at a distal portion thereof.
 16. A method, comprising:disposing an introducer sheath in the vasculature of a patient;introducing a catheter assembly into the proximal end of the introducersheath and into the vasculature through the introducer sheath, thecatheter assembly including an elongate body having an expandablecannula coupled with a distal end thereof, the catheter assembly havingan expandable impeller being journaled for rotation in the expandablecannula; expanding the expandable impeller for operation in a source ofblood; retracting the elongate body into the introducer sheath such thatthe expandable cannula engages a distal end of the introducer sheath;providing relative motion between the introducer sheath and theexpandable cannula to compress the expandable cannula; and removing theintroducer sheath and the catheter assembly from the patient.
 17. Themethod of claim 16, further comprising prior to retracting the elongatebody into the introducer sheath, retracting the impeller into theelongate body of the catheter assembly to compress the impeller.
 18. Themethod of claim , further retracing a retainer disposed over theexpandable cannula and expandable impeller after introducing thecatheter assembly to expand the expandable impeller.
 19. The method ofclaim 18, wherein the retainer comprises a separation zone disposedlongitudinally there along.
 20. The method of claim 19, furthercomprising separating first and second longitudinal portions of theseparation zone from each other to create a gap large enough for theelongate body of the catheter assembly to pass there through.